Since the Doppler histories of targets are different and can be treated as approximately linearly changing,the chirp rate,which is obtained from the time-chirp distribution of the echo by use of CLEAN,is used to separate the echo of each target.

To detect transient signals under complex background,a novel method of aliasing-free exponential bilinear time-frequency distribution is presented in this paper,which can avoid the frequency aliasing and information loss existing in the traditional bilinear distributions,reduce the crossterms effectively and possess high time-frequency resolution.